Nonwoven filtration media including microfibrillated cellulose fibers

ABSTRACT

A nonwoven filtration medium that includes a fibrous base media including synthetic and/or natural fibers and micro fibrillated cellulose fibers.

RELATED APPLICATIONS

This application is a U.S. National Stage Application of InternationalApplication No. PCT/US2014/020710, titled NONWOVEN FILTRATION MEDIAINCLUDING MICROFIBRILLATED CELLULOSE FIBERS, filed on Mar. 5, 2014,which claims the benefit under 35 U.S.C. § 119(e) of U.S. ProvisionalPatent Application No. 61/775,536 filed on Mar. 9, 2013 titled NONWOVENFILTRATION MEDIA INCLUDING MICROFIBRILLATED CELLULOSE FIBERS, each ofwhich are hereby incorporated by reference in their entirety.

BACKGROUND OF THE DISCLOSURE

In many nonwoven filtration media, large fibers are combined withsmaller fibers. The larger fibers provide a skeleton structure aroundwhich the smaller fibers form a matrix. This combination allows forstrength provided by the large fibers, with filtration efficiencyprovided by the smaller fibers. For certain of these include resins;however, this can add undesirable cost and reduction inporosity/permeability.

In some media, no resin is needed to hold the matrix together; however,one of the weaknesses of this type of design relates to the smallfibers, which typically do not have bonds to each other. Accordingly,the strength of the matrix of these small fibers is relatively weak andis largely dependent on the entanglement of the fibers themselves. Theseweak spots, although highly local and small, can allow the small fibersto move, which can lead to reduction in long term performance anddecreased durability.

SUMMARY

The present disclosure provides a nonwoven filtration medium thatincludes a fibrous base media including synthetic and/or natural fibersand microfibrillated cellulose fibers. Such microfibrillated cellulosefibers increase the strength and filtration efficiency of the fibrousbase media.

In one embodiment, a nonwoven filtration medium is provided thatincludes: a fibrous base media that includes synthetic and/or naturalfibers; and microfibrillated cellulose fibers; wherein a majority (i.e.,greater than 50%) of the microfibrillated cellulose fibers have alateral dimension of up to 4 microns.

In certain embodiments, the microfibrillated cellulose fibers are usedin an amount effective to enhance at least one property of the basemedia compared to the base media without the microfibrillated cellulosefibers. This means that the microfibrillated cellulose fibers are usedin an amount to simply enhance one or more properties already possessedby the base media. This also means that the microfibrillated cellulosefibers are used in an amount to provide the nonwoven filtration mediumwith one or more properties the base media fibers would not possesswithout the presence of the microfibrillated cellulose fibers. Thus,“enhancing” in this context means improving or creating one or moreproperties. Such properties include, for example, strength (e.g.,tensile strength or burst strength), efficiency, durability,processability, filtration efficiency, or combinations thereof.Preferably, such properties include strength and/or filtrationefficiency.

In another embodiment, a nonwoven filtration medium is provided thatincludes: a fibrous base media that includes synthetic and/or naturalfibers; and microfibrillated cellulose fibers, wherein a majority of themicrofibrillated cellulose fibers have a lateral dimension range of 700nm to 4 microns; wherein the microfibrillated cellulose fibers arepresent in an amount sufficient to provide a nonwoven filtration mediumhaving an average maximum load at break of at least 1.5 times that ofthe base media, and/or an average filtration efficiency that is at least10% greater than that of the base media.

In another embodiment, a nonwoven filtration medium is provided thatincludes: a base media that includes fiberglass fibers; andmicrofibrillated cellulose fibers, wherein a majority of themicrofibrillated cellulose fibers have a lateral dimension of up to 4microns.

In such embodiments, the “base media” is defined as a majority (i.e.,greater than 50%) of the total weight of filtration medium. The basemedia includes all components of the nonwoven filtration medium of thepresent disclosure, with the exception of the microfibrillated cellulosefibers.

Herein, “fibers” (whether in the context of the microfibrillatedcellulose fibers of the fibers of the base media) have an aspect ratio(i.e., length to lateral dimension) of greater than 3:1, and preferablygreater than 5:1. For example, fiberglass typically has an aspect ratioof greater than 100:1. In this context, the “lateral dimension” is thewidth (in 2 dimensions) or diameter (in 3 dimensions) of a fiber. Theterm “diameter” refers either to the diameter of a circularcross-section of as fiber, or to a largest cross-sectional dimension ofa non-circular cross-section of a fiber. Fiber lengths may be of finitelengths or infinite lengths, depending on the desired result.

For certain embodiments, if the base media fibers are synthetic, thesynthetic fibers have an average lateral dimension (typically, adiameter) of 0.5 micron to 30 microns. For certain embodiments, if thebase media fibers are natural (e.g., cellulose from flax, jute, hemp,wood, etc.), the natural fibers have an average lateral dimension(typically, a diameter) of greater than 10 microns. In this context, an“average” dimension refers to the average dimension of a sample of aplurality of fibers of the present disclosure.

In these embodiments, a layer of microfibrillated fibers can bemanufactured by forming a plurality of microfibrillated fibers on afibrous base media, thereby forming a filter medium (i.e., filtrationmedium). The filter medium (i.e., microfibrillated fibers plus fibrousbase media) can then be manufactured into filter elements (i.e.,filtration elements), including, e.g., flat-panel filters, cartridgefilters, or other filtration components.

The terms “comprises” and variations thereof do not have a limitingmeaning where these terms appear in the description and claims. Suchterms will be understood to imply the inclusion of a stated step orelement or group of steps or elements but not the exclusion of any otherstep or element or group of steps or elements. By “consisting of” ismeant including, and limited to, whatever follows the phrase “consistingof” Thus, the phrase “consisting of” indicates that the listed elementsare required or mandatory, and that no other elements may be present. By“consisting essentially of” is meant including any elements listed afterthe phrase, and limited to other elements that do not interfere with orcontribute to the activity or action specified in the disclosure for thelisted elements. Thus, the phrase “consisting essentially of” indicatesthat the listed elements are required or mandatory, but that otherelements are optional and may or may not be present depending uponwhether or not they materially affect the activity or action of thelisted elements.

The words “preferred” and “preferably” refer to embodiments of thedisclosure that may afford certain benefits, under certaincircumstances. However, other embodiments may also be preferred, underthe same or other circumstances. Furthermore, the recitation of one ormore preferred embodiments does not imply that other embodiments are notuseful, and is not intended to exclude other embodiments from the scopeof the disclosure.

In this application, terms such as “a,” “an,” and “the” are not intendedto refer to only a singular entity, but include the general class ofwhich a specific example may be used for illustration. The terms “a,”“an,” and “the” are used interchangeably with the term “at least one.”

The phrases “at least one of” and “comprises at least one of” followedby a list refers to any one of the items in the list and any combinationof two or more items in the list.

As used herein, the term “or” is generally employed in its usual senseincluding “and/or” unless the content clearly dictates otherwise. Theterm “and/or” means one or all of the listed elements or a combinationof any two or more of the listed elements.

Also herein, all numbers are assumed to be modified by the term “about”and preferably by the term “exactly.” As used herein in connection witha measured quantity, the term “about” refers to that variation in themeasured quantity as would be expected by the skilled artisan making themeasurement and exercising a level of care commensurate with theobjective of the measurement and the precision of the measuringequipment used.

Also herein, the recitations of numerical ranges by endpoints includeall numbers subsumed within that range as well as the endpoints (e.g., 1to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.). Herein, “up to” anumber (e.g., up to 50) includes the number (e.g., 50).

The above summary of the present disclosure is not intended to describeeach disclosed embodiment or every implementation of the presentdisclosure. The description that follows more particularly exemplifiesillustrative embodiments. In several places throughout the application,guidance is provided through lists of examples, which examples can beused in various combinations. In each instance, the recited list servesonly as a representative group and should not be interpreted as anexclusive list.

DRAWINGS

The disclosure may be more completely understood in connection with thefollowing drawings:

FIG. 1: Scanning electron microscopy (SEM) image of an exemplarynonwoven filtration medium of the present disclosure with arrowspointing towards examples of the microfibrillated cellulose fiberswithin the base all-cellulose media.

FIG. 2: Cross-sectional scanning electron microscopy (SEM) image of anexemplary nonwoven filtration medium of the present disclosure witharrows pointing towards examples of the microfibrillated cellulosefibers within the base all-cellulose media.

FIG. 3: Graphical summary of the tensile data showing increased maximumload at break with increasing amounts of microfibrillated cellulose(MFC).

FIG. 4: Comparison of tensile test curves for samples from Furnishes E-Hdemonstrating the higher elongation of the samples containingmicrofibrillated cellulose (MFC) as well as the increased maximum loadat break for samples containing MFC.

FIG. 5: A graph of TSI 3160 efficiency data for the two samplesdescribed in Table 6 showing an increase in efficiency for all particlesizes measured.

FIG. 6: Optical microscopy image of a 1% microfibrillated cellulosesample in water cast onto a glass slide and dried. This imagecorresponds with the fiber size data provided in FIG. 7.

FIG. 7: Summary of the lateral dimension of all fibers able to bevisually resolved and measured in the image provided in FIG. 6.

FIG. 8. Optical microscopy image of a 1% microfibrillated cellulosesample in water cast onto a glass slide and dried. This imagecorresponds with the fiber size data provided in FIG. 9.

FIG. 9. Summary of the lateral dimension of all fibers able to bevisually resolved and measured in the image provided in FIG. 8.

FIG. 10. Comparison of tensile strength and air permeability which showsincreased tensile strength with microfibrillated cellulose fibers atsimilar air permeability of samples made with micro-fiber glass.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present disclosure provides a nonwoven filtration medium thatincludes a fibrous base media including synthetic and/or natural fibersand microfibrillated cellulose fibers. Such microfibrillated cellulosefibers are used to enhance (i.e., improve at least one property of, orcreate at least one new property in) the fibrous base media. Suchproperties include, for example, strength (e.g., tensile strength orburst strength), efficiency, durability, processability, filtrationefficiency, or combinations thereof.

The fibrous “base media” forms a majority (i.e., greater than 50%) ofthe total weight of the nonwoven filtration medium. The base mediaincludes all components with the exception of the microfibrillatedcellulose.

In certain embodiments, the microfibrillated cellulose fibers are usedin an amount effective to enhance at least one property of the basemedia compared to the base media without the microfibrillated cellulosefibers. Typically, the microfibrillated cellulose fibers are present inthe nonwoven filtration medium in an amount of at least 1 weight percent(wt-%), or at least 2 wt-%, or at least 3 wt-%, based on the totalweight of the nonwoven filtration medium. The microfibrillated cellulosefibers are present in the nonwoven filtration medium in an amount of upto 49 wt-%, or up to 20 wt-%, or up to 18 wt-%, based on the totalweight of the nonwoven filtration medium.

The microfibrillated cellulose fibers can be disposed on a surface ofthe base media. Alternatively or additionally, the microfibrillatedcellulose fibers can be distributed throughout the base media.

Referring to FIGS. 1 and 2, which are scanning electron microscopy (SEM)images of exemplary nonwoven filtration media of the present disclosure,show the microfibrillated cellulose fibers (arrows) within the baseall-cellulose media. FIG. 2 is a cross-sectional image. In certainembodiments, the nonwoven filtration medium of the present disclosurehas a thickness of at least 100 microns, or at least 150 microns. Incertain embodiments, the nonwoven filtration medium of the presentdisclosure has a thickness of no greater than 4 inches (10.2 cm), or nogreater than 5 mm.

In certain embodiments, the nonwoven filtration medium of the presentdisclosure has a basis weight (g/m²) of at least 10, or at least 20, orat least 25, or at least 35 g/m². In certain embodiments, the nonwovenfiltration medium of the present disclosure has a basis weight (g/m²) ofup to 400, or up to 300, or up to 200, or up to 150 g/m². In certainembodiments, the nonwoven filtration medium of the present disclosurehas a basis weight (g/m²) of 25-300 g/m². In certain embodiments, thenonwoven filtration medium of the present disclosure has a basis weightof 35-150 g/m².

Microfibrillated cellulose (MFC) herein refers to that material asdefined by G. Chinga-Carrasco in Nanoscale Research Letters, 2011,6:417: “MFC materials may be composed of (1) nanofibrils, (2) fibrillarfines, (3) fibre fragments and (4) fibres. This implies that MFC is notnecessarily synonymous with microfibrils, nanofibrils or any othercellulose nano-structure. However, properly produced MFC materialscontain nano-structures as a main component, i.e. nanofibrils.” Thediameters (or, for the microfibrillated cellulose fibers, the “lateraldimensions”) of these components are reproduced in Table 1 of that samedocument and are as follows: (1) nanofibrils (<0.1 μm); (2) fibrillarfines (<1 μm); (3) fibres or fibre fragments (10 to 50 μm).

Furthermore, the term “microfibrillated cellulose,” as used herein, doesnot include dry ground cellulose (also referred to as micronizedcellulose or microfine cellulose) and does not include microcrystallinecellulose obtained by removing amorphous portions by acid hydrolysis, asdescribed in U.S. Pat. No. 5,554,287.

In certain embodiments, the microfibrillated cellulose fibers used donot have a “tree structure” (as described in U.S. Pat. Pub. No.2012/0043038) wherein the described fibrillation process causes externaland internal segments of the fiber surface to partially detach from themain fiber structure and become fibrils attached by one segment to themain fiber structure. Such fibrils provide more structure on the fiberto attach to other fibers in a paper structure, for example. For certainembodiments, this is not desirable.

Typically, useful microfibrillated cellulose fibers for the filtrationmedia of the present disclosure have a lateral dimension (e.g., width in2 dimensions) of up to 4 microns (μm). Typically, usefulmicrofibrillated cellulose fibers have a lateral dimension of at least700 nanometers (nm).

In certain embodiments of a nonwoven filtration medium of the presentdisclosure, a majority (i.e., greater than 50%) of the microfibrillatedcellulose fibers have a lateral dimension of up to 4 microns. In certainembodiments of a nonwoven filtration medium of the present disclosure, amajority (i.e., greater than 50%) of the microfibrillated cellulosefibers have a lateral dimension of 700 nm to 4 microns.

The microfibrillated cellulose fibers increase the strength, includingwet strength, and/or filtration efficiency of the base media, whetherused for air or liquid filtration. This occurs without the use of aresin (e.g., synthetic resin such as phenolics, acrylics), as is knownis certain filtration media, or with the use of reduced amounts of suchresins. In certain embodiments of the present disclosure, nonwovenfiltration media of the present disclosure include less than 15 wt-%, orless than 10 wt-%, or less than 5 wt-%, or less than 2 wt-% resin, basedon the total weight of the nonwoven filtration media. Generally, noresin is used in nonwoven filtration media of the present disclosure.

Furthermore, if other small fibers are used, such as fiberglass fibers,there is a reduction in the shedding of such small fibers.

Enhanced strength provided by the microfibrillated cellulose can bedemonstrated by the Tensile Test in the Examples Section. In certainembodiments, the nonwoven filtration medium possesses an average maximumload at break of at least 1.5 times that of the base media (without themicrofibrillated cellulose). In certain embodiments, the nonwovenfiltration medium possesses an average maximum load at break of at least2 times that of the base media (without the microfibrillated cellulose).In certain embodiments, the nonwoven filtration medium possesses anaverage maximum load at break of at least 3 times that of the base media(without the microfibrillated cellulose).

Enhanced strength provided by the microfibrillated cellulose can also bedemonstrated by the Burst Strength Test in the Examples Section. Incertain embodiments, the nonwoven filtration medium possesses an averagedry burst strength at least 25% higher than that of the base media(without the microfibrillated cellulose). In certain embodiments, thenonwoven filtration medium possesses measurable wet burst strength,where the base media cannot be measured for wet burst strength as itdoes not maintain enough structural integrity during the pre-test soakto allow it to be measured.

The filtration efficiency of filtration media of the present disclosureis characteristic of the filtration media and is related to the fractionof the particulate removed from the mobile fluid stream. Fluid in thisexample is a gas. Typically, such gas is air.

Enhanced filtration of air provided by the microfibrillated cellulosecan be demonstrated by the LEFS Test in the Examples Section. In certainembodiments, the nonwoven filtration medium possesses an averagefiltration efficiency that is at least 5% greater than that of the basemedia, according to the LEFS Test. In certain embodiments, the nonwovenfiltration medium possesses an average filtration efficiency that is atleast 10% greater than that of the base media, according to the LEFSTest. In certain embodiments, the nonwoven filtration medium possessesan average filtration efficiency that is at least 20% greater than thatof the base media, according to the LEFS Test. In certain embodiments,the nonwoven filtration medium possesses an average filtrationefficiency that is at least 50% greater than that of the base media,according to the LEFS Test. In certain embodiments, the nonwovenfiltration medium possesses an average filtration efficiency that is atleast 100% greater than that of the base media, according to the LEFSTest.

Enhanced filtration of air provided by the microfibrillated cellulosecan be demonstrated by the TSI 3160 Test in the Examples Section. Incertain embodiments, the nonwoven filtration medium possesses an averagefiltration efficiency that is at least 30% greater than that of the basemedia, according to the TSI 3160 Test. In certain embodiments, thenonwoven filtration medium possesses an average filtration efficiencythat is at least 50% greater than that of the base media, according tothe TSI 3160 Test. In certain embodiments, the nonwoven filtrationmedium possesses an average filtration efficiency that is at least 100%greater than that of the base media, according to the TSI 3160 Test.

Although the microfibrillated cellulose fibers enhance one or moreproperties of the base media, e.g., increase the strength of the fibrousbase media and/or increase the filtration efficiency of the fibrous basemedia, they can also decrease permeability. Although this is typicallyundesirable, reduced levels of permeability can be acceptable when allproperties are balanced.

Thus, the terms “filter media or medium” or “filtration media or medium”relate to a layer having at least minimal permeability and porosity suchthat it is at least minimally useful as a filter structure and is not asubstantially impermeable layer such as conventional paper, coated stockor newsprint made in a conventional paper making wet laid processes.

The fibrous “base media” forms a majority (i.e., greater than 50%) ofthe overall weight of the filtration medium. The fibers of the basemedia can be synthetic fibers, natural fibers, or a combination thereof.Preferably, such fibers are not fibrillated.

Exemplary synthetic fibers include polymeric fibers, such as polyolefins(e.g., polyethylene, polypropylene), polyamides (e.g., nylon),polyesters (e.g., polyethylene terephthalate), polyvinyl chloride,polyvinyl alcohol (of various degrees of hydrolysis), polyvinyl acetate,rayon, polyvinyl chloride acetate, polyvinyl butyral, acrylic resins(e.g., polyacrylate, polymethylacrylate, polymethylmethacrylate), polyvinylidene chloride, polystyrene, polyurethanes, synthetic cellulosicresins (e.g., cellulosic nitrate, cellulosic acetate, cellulosic acetatebutyrate, ethyl cellulose, etc.), copolymers of any of the abovematerials (e.g., ethylene-vinyl acetate copolymers, ethylene-acrylicacid copolymers, styrene-butadiene block copolymers, KRATON rubbers, andthe like). Other suitable synthetic fibers include cellulosic and otherfibers coated with thermoplastic polymers, and multi-component fibers inwhich at least one of the components includes a thermoplastic polymer.Typical thermoplastic polymers include polyolefins, e.g., polyethylene,polypropylene, polybutylene, and copolymers thereof, and polyesters suchas polyethylene terephthalate.

Single and multi-component fibers (e.g., bicomponent fibers) can be usedin the base media of the filtration medium of the present disclosure.Such fibers can include, for example, polyester, polyethylene,polypropylene, and other conventional thermoplastic fibrous materials.The physical configuration of a bicomponent fiber is typically in aside-by-side or sheath-core structure. In side-by-side structure, thetwo resins are typically extruded in a connected form in a side-by-sidestructure. In a sheath-core structure, the material with the lowerinciting point typically forms the sheath. It is also possible to alsouse lobed fibers where the tips have lower melting point polymer. Thepolymers of bicomponent (sheath/core or side-by-side) fibers can be madeup of different thermoplastic materials, such as for example,polyolefin/polyester (sheath/core) bicomponent fibers whereby thepolyolefin, e.g. polyethylene sheath, melts at a temperature lower thanthe core, e.g., polyester.

Inorganic fibers, such as glass fibers (i.e., fiberglass), ceramicfibers, or basalt fibers can be used in the base media. Such inorganicfibers (particularly glass fibers) can be used alone in the base media,or used with other synthetic and/or natural fibers. For example, glassfibers can be used with larger fibers in the base media.

Typically, if used, glass fibers are present in the base media in anamount of at least 10 wt-%, or at least 20 wt-%, based on the totalweight of the base media. Also, if used, glass fibers are present in thebase media in an amount of up to 80 wt-%, or up to 50 wt-%, based on thetotal weight of the base media.

The base media can include combinations of various fibers of differentcomposition and/or different sizes. In certain embodiments, the basemedia includes fiberglass and synthetic fibers other than fiberglass.

Glass fiber media and bicomponent fiber media that can be used as thebase media are disclosed in, for example, U.S. Pat. Nos. 7,309,372,7,314,497, and U.S. Pat. Pub. No. 2006/0096932.

For certain embodiments, if the base media fibers are synthetic, thesynthetic fibers have an average lateral dimension (typically, adiameter) of at least 0.5 micron (i.e., 500 nm), and often at least 1micron. For certain embodiments, if the base media fibers are synthetic,the synthetic fibers have an average lateral dimension (typically, adiameter) of no greater than 30 microns, no greater than 20 microns, andoften no greater than 15 microns. Typically, fiberglass fibers have alateral dimension of at least 500 nm, and often no greater than 20microns.

Exemplary natural fibers include cellulose, cotton, sisal, kenaf,bamboo, sugarcane, coconut, flax, jute, hemp, wood.

In certain embodiments, the base media includes cellulose fibers,obtained, for example, from flax, jute, hemp, wood, cotton, kenaf, etc.Although available from other sources, cellulosic fibers are derivedprimarily from wood pulp. Suitable wood pulp fibers for use in the basemedia described herein can be obtained from well-known chemicalprocesses such as the Kraft and sulfite processes, with or withoutsubsequent bleaching. Pulp fibers can also be processed bythermo-mechanical, chemi-thermo-mechanical methods, or combinationsthereof. The preferred pulp fiber is produced by chemical methods.Ground wood fibers (which is distinct from the dry ground cellulosereferred to as micronized cellulose or microfine cellulose), recycled orsecondary wood pulp fibers, and bleached and unbleached wood pulp fiberscan be used. Softwoods and hardwoods can be used. Details of theselection of wood pulp fibers are well-known to those skilled in theart. These fibers are commercially available from a number of companies.The wood pulp fibers can also be pretreated prior to use. Thispretreatment may include physical or chemical treatment, such ascombining with other fiber types, subjecting the fibers to steam, orchemical treatment, for example, crosslinking the cellulose fibers usingany one of a variety of known crosslinking agents, which increase fiberbulk and resiliency.

For certain embodiments, if the base media fibers are natural, thenatural fibers have an average lateral dimension (typically, a diameter)of greater than 10 microns. Typically, cellulose fibers typically have alateral dimension of at least 20 microns, and often up to 50 microns.

In certain embodiments, the fibrous base media does not includecellulose acetate fibers.

Fibers of the base media can be pre-treated. Examples of pre-treatingfibers include the application of surfactants or other liquids whichmodify the surface chemistry of the fibers. Other pretreatments includeincorporation of antimicrobials, pigments, dyes and densification orsoftening agents. Fibers pre-treated with other chemicals, such asthermoplastic and thermosetting resins also may be used. Combinations ofpre-treatments also may be employed. Similar treatments can also beapplied after the composite formation (microfibrillated fibers combinedwith the fibrous base media) in post-treatment processes.

The microfibrillated cellulose fibers can be made using conventionaltechniques. For example, microfibrillated cellulose can be made by theprocess disclosed in U.S. Pat. Pub. No. 2009/0221812. Briefly, thisinvolves cellulose pulp being treated with a small amount of a wooddegrading cellulase enzyme followed by high shear processing using amicrofluidizer. Processing in the microfluidizer can be performed atpressures from 5000 pounds per square inch (psi) to 30000 psi usinginteraction chambers in a microfluidizer with sizes of 87, 100, and 200μm using 1 to 3 passes through the equipment. Preferably, processingoccurs using 1 pass through a 200-μm chamber at 5000 psi to 8000 psi.

In preferred embodiments, southern softwood cellulose microfibrillatedfibers can be obtained by first enzyme treating the cellulose,denaturing of the enzyme using heat, and processing with high shearprocessing equipment. Fiber size can be controlled by processingconditions, i.e., smaller interaction chamber size, more passes throughthe microfluidizer and/or higher operating pressure gives smallerfibers.

Base media of the nonwoven filtration media described herein can be beenmade by a wide variety of known methods. For example, this can includeelectrospinning, solution spinning, melt spinning, extrusion meltspinning, wet spinning, dry spinning, gel spinning, air-laid processing,wet-laid processing, melt-blowing, rotary attenuation, or flameattenuation. How such fibers are made is not intended to limit thenonwoven filtration medium of the present disclosure.

A plurality of microfibrillated fibers can be deposited on a surface ofthe fibrous base media, thereby forming a filter medium (i.e.,filtration medium). This can be done by methods such as spray coating,spin coating, or wet-laid processing.

Alternatively, a plurality of microfibrillated fibers can beincorporated within (i.e., distributed throughout) the fibrous basemedia, thereby forming a filter medium (i.e., filtration medium). Thiscan be done by methods such as wet-laid or air-laid processing.

The filter medium (i.e., microfibrillated fibers plus fibrous basemedia) can then be manufactured into air or liquid filter elements(i.e., filtration elements), including, e.g., flat-panel filters,cartridge filters, or other filtration components. Examples of suchfilter elements are described in U.S. Pat. Nos. 6,746,517; 6,673,136;6,800,117; 6,875,256; 6,716,274; and 7,316,723. The shape and structureof the filter material, however, is typically selected by the designengineer and depends on the particular filtration application.

Exemplary Embodiments

1. A nonwoven filtration medium comprising:

-   -   a fibrous base media comprising synthetic and/or natural fibers;        and    -   microfibrillated cellulose fibers, wherein a majority of the        microfibrillated cellulose fibers have a lateral dimension of up        to 4 microns.        2. The nonwoven filtration medium of embodiment 1 wherein:    -   if the base media fibers are synthetic, the synthetic fibers        have an average diameter of 0.5 micron to 30 microns; and    -   if the base media fibers are natural, the natural fibers have an        average lateral dimension of greater than 10 microns.        3. The nonwoven filtration medium of embodiment 1 or 2 wherein        the microfibrillated cellulose fibers have a lateral dimension        of 700 nm to 4 microns.        4. The nonwoven filtration medium of any of embodiments 1        through 3 wherein the microfibrillated cellulose fibers are used        in an amount effective to enhance at least one property of the        base media compared to the base media without the        microfibrillated cellulose fibers.        5. The nonwoven filtration medium of embodiment 4 wherein the at        least one property is selected from strength (e.g., tensile        strength or burst strength), efficiency, durability,        processability, filtration efficiency, or combinations thereof.        6. The nonwoven filtration medium of embodiment 5 wherein the        microfibrillated cellulose fibers are used in an amount        effective to increase the strength and/or filtration efficiency        of the base media.        7. The nonwoven filtration media of any of embodiments 1 through        6 wherein the microfibrillated cellulose fibers are present in        an amount of 1 wt-% to 49 wt-%.        8. The nonwoven filtration media of any of embodiments 1 through        7 wherein the microfibrillated cellulose fibers are disposed on        a surface of the base media.        9. The nonwoven filtration media of any of embodiments 1 through        8 wherein the microfibrillated cellulose fibers are distributed        throughout the base media.        10. The nonwoven filtration medium of any of embodiments 1        through 9 wherein the base media comprises cellulose fibers.        11. The nonwoven filtration medium of embodiment 10 wherein the        cellulose fibers in the base media have a lateral dimension of        20 microns to 50 microns.        12. The nonwoven filtration medium of any of embodiments 1        through 11 wherein the base media comprises synthetic fibers.        13. The nonwoven filtration medium of embodiment 12 wherein the        synthetic fibers have a lateral dimension of 1 micron to 15        microns.        14. The nonwoven filtration medium of any of embodiments 1        through 13 wherein the base media comprises fiberglass.        15. The nonwoven filtration medium of embodiment 14 wherein the        base media fiberglass fibers have a lateral dimension of 500 nm        to 20 microns.        16. The nonwoven filtration medium of embodiment 1 wherein the        base media comprises fiberglass and synthetic fibers other than        fiberglass.        17. The nonwoven filtration medium of any of embodiments 14        through 16 wherein the fiberglass is present in the base media        in an amount of 10 wt-% to 80 wt-%, based on the total weight of        the base media.        18. The nonwoven filtration medium of embodiment 17 wherein the        fiberglass is present in the base media in an amount of 20 wt-%        to 50 wt-%, based on the total weight of the base media.        19. The nonwoven filtration medium of any of embodiments 1        through 18 which possesses an average maximum load at break of        at least 1.5 times that of the base media according to the        Tensile Test.        20. The nonwoven filtration medium of embodiment 19 which        possesses an average maximum load at break of at least 2 times        that of the base media.        21. The nonwoven filtration medium of embodiment 20 which        possesses an average maximum load at break of at least 3 times        that of the base media.        22. The nonwoven filtration medium of any of embodiments 1        through 21 which possesses an average filtration efficiency that        is at least 5% greater than that of the base media, according to        the LEFS Test.        23. The nonwoven filtration medium of embodiment 22 which        possesses an average filtration efficiency that is at least 10%        greater than that of the base media.        24. The nonwoven filtration medium of embodiment 23 which        possesses an average filtration efficiency that is at least 20%        greater than that of the base media.        25. The nonwoven filtration medium of any of embodiments 1        through 24 which possesses an average dry burst strength at        least 25% higher than that of the base media according to the        Burst Strength Test.        26. The nonwoven filtration medium of any of embodiments 1        through 25 suitable for air filtration.        27. The nonwoven filtration medium of any of embodiments 1        through 26 suitable for liquid filtration.        28. The nonwoven filtration medium of any of embodiments 1        through 27 which has a thickness of at least 100 microns.        29. A nonwoven filtration medium comprising:    -   a base media comprising synthetic and/or natural fibers; and    -   microfibrillated cellulose fibers, wherein a majority of the        microfibrillated cellulose fibers have a lateral dimension of        700 nm to 4 microns;    -   wherein the microfibrillated cellulose fibers are present in an        amount sufficient to provide a nonwoven filtration medium having        an average maximum load at break of at least 1.5 times that of        the base media, and/or an average filtration efficiency that is        at least 10% greater than that of the base media.        30. The nonwoven filtration medium of embodiment 29 wherein:    -   if the base media fibers are synthetic, the synthetic fibers        have an average diameter of 0.5 micron to 30 microns; and    -   if the base media fibers are natural, the natural fibers have an        average lateral dimension of greater than 10 microns.        31. The nonwoven filtration medium of embodiment 29 or 30        wherein the base media comprises fiberglass.        32. The nonwoven filtration media of any of embodiments 29        through 31 wherein the microfibrillated cellulose fibers are        disposed on a surface of the base media.        33. The nonwoven filtration media of any of embodiments 29        through 32 wherein the microfibrillated cellulose fibers are        distributed throughout the base media.        34. The nonwoven filtration medium of any of embodiments 29        through 33 wherein the base media comprises cellulose fibers.        35. The nonwoven filtration medium of embodiment 34 wherein the        cellulose fibers in the base media have a lateral dimension of        20 microns to 50 microns.        36. The nonwoven filtration medium of any of embodiments 29        through 35 wherein the base media comprises synthetic fibers.        37. The nonwoven filtration medium of embodiment 36 wherein the        synthetic fibers have a lateral dimension of 1 micron to 15        microns.        38. The nonwoven filtration medium of any of embodiments 29        through 37 wherein the base media comprises fiberglass.        39. The nonwoven filtration medium of embodiment 38 wherein the        base media fiberglass fibers have a lateral dimension of 500 nm        to 20 microns.        40. A nonwoven filtration medium comprising:    -   a base media comprising fiberglass fibers; and    -   microfibrillated cellulose fibers, wherein a majority of the        microfibrillataed cellulose fibers have a lateral dimension        range of up to 4 microns.        41. The nonwoven filtration medium of embodiment 40 wherein:    -   if the base media fibers are synthetic, the synthetic fibers        have an average diameter of 0.5 micron to 30 microns; and    -   if the base media fibers are natural, the natural fibers have an        average lateral dimension of greater than 10 microns.        42. The nonwoven filtration medium of embodiment 41 wherein the        microfibrillated cellulose fibers have a lateral dimension of        700 nm to 4 microns.        43. The nonwoven filtration medium of any of embodiments 40        through 42 wherein the microfibrillated cellulose fibers are        used in an amount effective to enhance at least one property of        the base media compared to the base media without the        microfibrillated cellulose fibers.        44. The nonwoven filtration medium of embodiment 43 wherein the        at least one property is selected from strength (e.g., tensile        strength or burst strength), efficiency, durability,        processability, filtration efficiency, or combinations thereof.        45. The nonwoven filtration medium of embodiment 44 wherein the        microfibrillated cellulose fibers are used in an amount        effective to increase the strength and/or filtration efficiency        of the base media.        46. A filter element comprising a nonwoven filtration medium of        any of embodiments 1 through 45.

Examples

Objects and advantages of this disclosure are further illustrated by thefollowing examples, but the particular materials and amounts thereofrecited in these examples, as well as other conditions and details,should not be construed to unduly limit this disclosure.

Fibers:

Southern softwood cellulose microfibrillated fibers were obtained byfirst enzyme treating the cellulose, denaturing of the enzyme usingheat, and processing with high shear processing equipment atMicrofluidics Corp., Newton, Mass. Fibers ranged in size from hundredsof nanometers to tens of microns in diameter. Fiber size can becontrolled by processing conditions, i.e., smaller interaction chambersize, more passes through the microfluidizer and/or higher operatingpressure gives smaller fibers. The optical microscopy images were takenon films cast from a dilute solution of the microfibrillated celluloseonto a glass slide and dried. A large range of fiber sizes can be seen,including fibers in the target range of approximately 0.7-4 microns (μm)in diameter. Higher magnification images do show fibers below 0.5 μm indiameter, but as smaller fibers are more likely to hydrogen bond to eachother, it is difficult to resolve anything below approximately 200 nm.

Experimental Procedure for Making the Microfibrillated Cellulose:

Softwood cellulose pulp was added to water to make a 1% by weightsolution. The solution was stirred using an overhead mixer for 2 hours.(Ann-speed of the mixer not important, just the fact that there isagitation) The cellulose solution was covered and left overnight at roomtemperature. The following day 0.01% of a Trichoderma reesei cellulaseenzyme solution was added to the cellulose solution; the solution washeated to 50° C. and stirred with the overhead mixer for 2 hours. Thetemperature was increased to and held at 80° C. for approximately 20minutes to stop the enzyme activity.

This enzyme-treated 1% softwood cellulose pulp solution was thenprocessed using a Microfluidics M-110EH processer as described in theliterature (e.g., U.S. Pat. Pub. No. 2009/0221812). Pressures of 5000pounds per square inch (psi), 8000 psi, or 10,000 psi were used withsamples passing through one or two 200-μm chambers one time. Regardlessof these specified pressures, the resultant microfibrillated cellulosefunctioned essentially the same. The processed fibers were collectedfrom the M-110EH and used in hand sheet formulations.

Methods Used for Data Collection:

Fiber sizing was performed as described in greater detail below.

Permeability relates to the amount of air (ft/min) that will flowthrough a filter medium at a pressure drop of 0.5 inch of water. Ingeneral, permeability is measured using a Frazier Permeability Tester(TexTest 3300) available from Advanced Testing Instrument Corp (ATI).

LEFS Test—LEFS (filtration) efficiency is described as the efficiencymeasured according to ASTM No. 1215-89, with 0.78-μm monodispersepolystyrene spherical particles, at 20 feet per minute (fpm).

TSI 3160 Test—the 3160 (filtration) efficiency is tested using a TSIAutomated Filter Tester 3160 using monodisperse aerosol particles0.1-0.4 μm at 16 fpm.

Tensile testing was performed on a Thwing Albert EJA Universal MaterialsTester using a 1-inch wide, 4-inches long sample at a constant speed of2 inches per minute (in/min). When “tensile” data is presented in thetables, the value provided is the maximum force at break for the sample.Burst strength testing was performed using a Mullen-type bursting tester(Testing Machines Inc.) according to TAPPI method 403. Wet burst testingadded a 1-minute soak in water containing 3% surfactant prior to testingaccording to the method.

Basic Handsheet Sample Formation Procedure:

Materials were selected and weighed into individual containers such asplastic or aluminum weigh boats. The mass of the materials aredetermined from the from target basis weight of the final handsheetsample, the area of the handsheet former, and the ratio of theindividual materials that make up the sample handsheet. The handsheetformer used is a 30 cm×30 cm gravity pull handsheet former manufacturedby Adirondack Machine Corporation. Three common mechanical dispersionmethods are used to assist with the dispersion of the fibers. A Waringblender, TAPPI Pulp Disintegrator, and/or low speed laboratory mixer maybe used to disperse the fiber materials. Different fibers can havevarying dispersion properties in tap water. Therefore, chemicaladditives can be added to the water/fiber mixture to improve dispersionand/or suspension of the fibers in the water. These additives can beused to improve the formation of the media by adjusting the pH, thewater surface tension, and/or the water viscosity. After the fibers aredispersed, the fiber/water mixture is poured into the handsheet formerthat has already been filled ¾ of its volume with tap water and has hada screen or scrim placed on the bottom of the former. The mixture isthen slightly mixed to ensure the fibers are homogeneous throughout thehandsheet former. Immediately following this, a valve is opened up belowthe screen, allowing the water to flow out the bottom of the handsheetformer with the fibers being collected on the screen or scrim. The boxis opened and the sheet along with its screen or scrim are carefullyremoved and dried, first using a vacuum slit to remove excess water,then placed in an Emerson Speed Dryer hot plate and generally dried atapproximately 210° F. for 5 minutes. The temperature and time in thehotplate can be adjusted based on the materials in the media. A personskilled in the art will have the ability to effectively use theseadditives, mechanical dispersion methods, and drying techniques to formhomogeneous handsheet samples.

Example Sheet with Hardwood/Softwood Blend:

The example sheet “Furnish C” was made by first weighing out 3.89 grams(g) each of Suzano Eucalyptus hardwood pulp and Robor Flash NorthernSoftwood pulp. The Suzano Eucalyptus was placed in a blender with 750milliliters (mL) hot tap water and agitated for 90 seconds to break upthe pulp prior to adding it to the disintegrator blender along with 1.5liters (L) of tap water, the Robor Flash Northern softwood and 1.25 mLof acetic acid in the form of household vinegar. The disintegrator wasrun for 8000 revolutions, 86 mL of the 1% aqueous solution ofmicrofibrillated cellulose was added, and the disintegrator turned onfor 1000 more revolutions. This mixture was added to a head box that hada scrim covering the bottom screen and filled approximately ¾ of the waywith tap water. Agitation was done using a plunger to ensure the fiberswere well blended and the water was then drained. Once the water haddrained, the box was opened, the sheet along with its scrim wascarefully removed, passed over a vacuum slot 3× for removal of theexcess water, then dried for approximately 3 min/side in a Emerson SpeedDryer at approximately 200° F. The dried sheet was left on the scrimuntil the sheet underwent testing.

The example sheets “Furnish A,” “Furnish B,” and “Furnish D” were madein a similar fashion using the amounts of materials listed in Table 1.

Data provided in Table 2 show the increased strength and LEFS efficiencyof the hand sheets containing microfibrillated cellulose. The basisweight results also show that a minimum of the microfibrillatedcellulose fibers were lost during sheet formation, which is many times aconcern when using fibers in this size range in a wet-laid process.

TABLE 1 Furnish information for handsheets comprised of hardwood,softwood and microfibrillated cellulose. Suzano Robor Flash 1% aqueousTarget Eucalyptus Northern microfibrillated Basis Hardwood Softwoodcellulose Weight (g) (g) solution (mL) (g/m²) Furnish A 4.32 4.32 — 90Furnish B 4.06 4.06 52 90 Furnish C 3.89 3.89 86 90 Furnish D 3.72 3.72121 90

TABLE 2 Summarized data collected on the handsheets made according tothe furnish information provided in Table 1. Basis Perme- Thick- Dry MaxWeight ability ness LEFS Tensile Burst Pore (g/m²) (ft/min) (mm)Efficiency (kg/in) (psi) (μm) Furnish A 92 53 0.49 38 0.4 8.9 74 FurnishB 90 40 0.48 36 0.8 8.9 72 Furnish C 93 32 0.49 40 1.1 8.9 67 Furnish D86 26 0.46 42 1.5 8.8 69Example Sheet with all Softwood:

The example sheet “Furnish F” was made by first weighing out 11.16 g ofSouthern Softwood pulp. The pulp was placed with 2.5 L of tap water and1.25 mL of acetic acid in the form of household vinegar into a pulpdisintegrator. The disintegrator was run for 8000 revolutions, 36 mL ofthe 1% aqueous solution of microfibrillated cellulose was added, and thepulp disintegrator turned on for 1000 more revolutions. This mixture wasadded to a head box that had a scrim covering the bottom screen andfilled ¾ of the way with tap water. Agitated was done using a plunger toensure the fibers were well blended and the water was then drained. Oncethe water had drained, the box was opened, the sheet along with its'scrim was carefully removed, passed over a vacuum slot 3× for removal ofthe excess water, then dried for 5 min/side in a Emerson Speed Dryer at200° F. The dried sheet is left on the scrim until the sheet undergoestesting.

The sheets of “Furnish E” and “Furnish G” and Furnish H were made in asimilar fashion using the amounts of materials listed in Table 3.

The sheets with microfibrillated cellulose showed increased maximumforce at break as well as increased LEFS efficiency (see the dataprovided in Table 4. Sheets of “Furnish E” and “Furnish G” were alsotested for wet burst strength. Furnish G was able to be measured and hada wet burst strength of 9 psi, furnish E was not able to be measured forwet burst as it came apart during the 1 min. soak procedure prior to themeasurement.

TABLE 3 Furnish information for handsheets comprised of softwood andmicrofibrillated cellulose. 1% aqueous Target Southern microfibrillatedBasis Softwood cellulose solution Weight (g) (mL) (g/m²) Furnish E 11.52— 128 Furnish F 11.16 36 128 Furnish G 10.80 72 128 Furnish H 10.08 144128

TABLE 4 Summarized data collected on the handsheets made according tothe furnish information provided in Table 3. Basis Max WeightPermeability Thickness LEFS Tensile Pore (g/m²) (ft/min) (mm) Efficiency(kg/in) (μm) Furnish E 126 32 0.71 30 1.1 83 Furnish F 124 25 0.68 341.8 74 Furnish G 124 21 0.66 34 2.4 76 Furnish H 125 15 0.66 38 3.2 69

FIG. 3 shows the graphical summary of the tensile data showing increasedmax load at break with increasing amounts of microfibrillated cellulose(MFC) provided in Table 4. The legend in FIG. 4 shows the furnish namesthat correspond with the percentage of MFC used in each furnish.

FIG. 4 shows a comparison of tensile test curves for samples fromFurnishes E-H demonstrating the higher elongation of the samplescontaining microfibrillated cellulose (MFC) as well as the increasedmaximum load at break for samples containing MFC.

Example with Resin Application:

Phenolic resin in the amounts indicated in Table 5 was applied to handsheets made with the Furnish E and G formulations. The sheet was passedone time through the tray of resin, squeezed through a set of rollers toremove excess resin, dried in a 250° F. oven for 10 min to dry, weighedfor calculation of resin uptake and finally cured for 10 min in a 300°F. oven. It can be seen in Table 5 that the some of the benefit ofmicrofibrillated cellulose (MFC) on tensile strength remain followingthe addition of resin, indicating the use of MFC as an option to reducefinal resin content of cellulose filtration media.

TABLE 5 Summary data for samples of base media and media containingmicrofibrillated cellulose (MFC) impregnated with a phenolic resin.Sample formulations are provided in Table 3. Max Average Pore SampleSample Permeability Size Tensile Formulation Description (fpm) (μm)(kgs/in) Furnish E All Softwood 33 83 1 Furnish E Softwood with  15%resin 32 82 7 Furnish E Softwood with  24% resin 32 81 11 Furnish GSoftwood with 6.3% MFC, no resin 20 81 2 Furnish G Softwood with 6.3%MFC,  16% resin 19 73 9 Furnish G Softwood with 6.3% MFC,  27% resin 2486 14Example with MFC as an Add-on Layer to an all-Cellulose Media:

An all-cellulose media containing resin was used as a base layer for thedeposition of microfibrillated cellulose. The procedure is the same asmaking a standard handsheet with the cellulose media replacing the scrimat the bottom of the head box. For Add-on Sample A, 60 mL of the 1%aqueous solution of microfibrillated cellulose (with a goal of 5 g/m²addition of basis weight) was added to approximately 2.5 L of water inthe pulp disintegrator and agitated for 1000 revolutions. This mixturewas added to a head box that had the base media covering the bottomscreen and filled ¾ of the way with tap water. Agitation was done usinga plunger to ensure the fibers were well blended and the water was thendrained. Once the water had drained the box was opened; the media wascarefully removed, passed over a vacuum slot 1× for removal of theexcess water, and dried for 5 min/side in an Emerson Speed Dryer atapproximately 200° F. The base media was wet with water for 10 min.,passed over the vacuum slot 1 time and dried 5 min/side in an EmersonSpeed Dryer at approximately 200° F. to mimic the treatment received bythe sheet with MFC deposited on top.

Table 6 and FIG. 5 demonstrate that the sample with the microfibrillatedcellulose resulted in higher efficiencies with efficiency measurementsusing particles from 0.1-0.4 μm (TSI3160 test, FIG. 5) as well as 0.8 μm(LEFS test, Table 6). The microfibrillated cellulose also providedmeasurable improvement in all strength measurements including tensileand wet burst strength.

TABLE 6 Summarized data collected on the sheets made according to thedescription of microfibrillated cellulose (MFC) as an add-on layer to anall-cellulose media. The data shows the increase in LEFS efficiency andwet burst strength with the addition of MFC. Machine Cross Perme-Direction Direction Wet Max Mass ability LEFS tensile tensile Burst Pore(g) (ft/min) Efficiency (kg/in) (kg/in) (psi) (μm) Base 7.2 28 18 11 7 858 Media Add-on 7.5 8 34 12 8 10 54 SampleFiber Size Data:

Fiber sizing was performed on samples prepared by diluting the 1%microfibrillated cellulose solution by approximately 10 times in water,placing a few drops of this solution onto a glass slide and allowing thesample to dry. The slides were imaged using a calibrated opticalmicroscope and the apparent lateral dimensions of the fibers weremeasured manually using ImageJ image analysis software. As many fibersas could be visually resolved were measured for their apparent lateraldimension and the data was compiled into histogram format. Examples ofresults are shown in FIGS. 6-9

FIG. 6 is an optical microscopy image of an MFC sample cast onto a glassslide. This image corresponds with the fiber size data provided in FIG.7.

FIG. 7 is a summary of the lateral dimension of all fibers able to bevisually resolved and measured in the image provided in FIG. 6.

FIG. 8 is an optical microscopy image of an MFC sample cast onto a glassslide. This image corresponds with the fiber size data provided in FIG.9.

FIG. 9 is a summary of the lateral dimension of all fibers able to bevisually resolved and measured in the image provided in FIG. 8.

Example of MFC with Polyester Bicomponent Fibers and Micro-Fiber GlassMixtures

A specific type of resin-free media design uses a combination ofpolyester bicomponent fibers and micro-fiber glass. The sheath of thebicomponent fibers will melt at a lower temperature than the core. Thisallows the bicomponent fibers to form a strong skeleton structure tohold together in sheet form the bicomponent and micro-fiber glass fiberswithout using resin to hold the fibers together. The micro-fiber glassfibers are needed to provide high filtration efficiencies.

Microfibrillated cellulose fibers have the ability to improve thestrength of this design type of resin-free filter media. Themicrofibrillated cellulose (MFC) fibers are of similar sizes to theglass fibers, and thus have the ability to integrate into the glassfiber matrix that exists between the bicomponent fibers. Thisintegration into the glass fiber matrix allows increased media strengthproperties, specifically tensile strength, without significantlyimpacting other media physical properties, specifically airpermeability.

In the following examples, the micro-fiber glass is replaced bydifferent amounts of MFC into the design of a resin free media design ofpolyester bicomponent fibers and micro-fiber glass. The addition of MFCinto the design shows significant increase in tensile strength of thefilter media.

The addition of any different fiber to a filter media design will verylikely change several of its physical properties. Therefore, to be ableto get a reasonable judgment of the effect of the MFC fiber, a secondset of samples was produced with the similar replacement of the mainmicro-fiber glass (see Table 7), but this time with a different type ofmicro-fiber glass. Both sets of samples show similar physicalproperties, specifically air permeability, but the samples withincreasing MFC fibers show significant increase in tensile strength (seeTable 8).

TABLE 7 Furnish design information for samples made with polyesterbicomponent fibers and micro-fiber glass. Advansa Micro- 271Pfibrillated 2 d × 6 mm Lauscha Lauscha Cellulose Target Polyester B-15-FB-04-F (1% water Sample Basis Bicomponent¹ Micro-Glass² Micro-Glass²solution) Formulation Weight Ratio Mass Ratio Mass Ratio Mass RatioVolume Furnish D0 48 g/m² 50% 2.16 g   50% 2.16 g ~ ~ ~ ~ Furnish DA1 48g/m² 50% 2.16 g 43.7% 1.89 g ~ ~  6.3% 27 mL Furnish DA2 48 g/m² 50%2.16 g 37.5% 1.62 g ~ ~ 12.5% 54 mL Furnish DA3 48 g/m² 50% 2.16 g 31.2%1.35 g ~ ~ 18.8% 81 mL Furnish DB1 48 g/m² 50% 2.16 g 43.7% 1.89 g  6.3%0.27 g ~ ~ Furnish DB2 48 g/m² 50% 2.16 g 37.5% 1.62 g 12.5% 0.54 g ~ ~Furnish DB3 48 g/m² 50% 2.16 g 31.2% 1.35 g 18.8% 0.81 g ~ ~ ¹Fibersavailable from Advansa, Caldenhofer Weg 192, 59063 Hamm, Germany ²FibersAvailable from Lauscha Fiber International Corp., 105 Eastport Lane,Summerville, SC 29483

TABLE 8 Physical properties of samples from Table 7. Sample Air TensileFormulation Permeability Strength Furnish D0 42.9 cfm 1.9 lbs/in FurnishDA1 36.0 cfm 3.0 lbs/in Furnish DA2 24.3 cfm 4.1 lbs/in Furnish DA3 21.7cfm 4.9 lbs/in Furnish DB1 35.7 cfm 1.4 lbs/in  urnish DB2 26.9 cfm 1.7lbs/in Furnish DB3 21.2 cfm 1.7 lbs/in

FIG. 10 shows a comparison of tensile strength and air permeability.This demonstrates an increased tensile strength with MFC fibers atsimilar air permeability of samples made with micro-fiber glass.

The complete disclosures of the patents, patent documents, andpublications cited herein are incorporated by reference in theirentirety as if each were individually incorporated. While the disclosureis susceptible to various modifications and alternative forms, specificsthereof have been shown by way of example and drawings, and will bedescribed in detail. It should be understood, however, that thedisclosure is not limited to the particular embodiments described. Onthe contrary, the intention is to cover modifications, equivalents, andalternatives falling within the spirit and scope of the disclosure.

The invention claimed is:
 1. A nonwoven filtration medium comprising: afibrous base media comprising synthetic and/or natural fibers; andmicrofibrillated cellulose fibers disposed on a surface of the basemedia, wherein the microfibrillated cellulose fibers are not distributedthroughout the base media, and wherein a majority of themicrofibrillated cellulose fibers have a lateral dimension of up to 4microns.
 2. The nonwoven filtration medium claim 1 wherein themicrofibrillated cellulose fibers have a lateral dimension of 700 nm to4 microns.
 3. The nonwoven filtration medium of claim 1 wherein themicrofibrillated cellulose fibers are used in an amount effective toincrease the strength and/or filtration efficiency of the base mediacompared to the base media without the microfibrillated cellulosefibers.
 4. The nonwoven filtration medium of claim 1 wherein themicrofibrillated cellulose fibers are present in an amount of 1 wt-% to49 wt-% based on the total weight of the nonwoven filtration medium. 5.The nonwoven filtration medium of claim 1 wherein the base mediacomprises cellulose fibers.
 6. The nonwoven filtration medium of claim 1wherein the base media comprises synthetic fibers.
 7. The nonwovenfiltration medium of claim 1 wherein the base media comprisesfiberglass.
 8. The nonwoven filtration medium of claim 7 wherein thebase media comprises fiberglass and synthetic fibers other thanfiberglass.
 9. The nonwoven filtration medium of claim 1 which possessesenhanced strength relative to that of the base media.
 10. The nonwovenfiltration medium of claim 1 which possesses an average filtrationefficiency that is at least 5% greater than that of the base media,according to the LEFS Test.
 11. The nonwoven filtration medium of claim1 suitable for air or liquid filtration.
 12. A filter element comprisinga nonwoven filtration medium of claim
 1. 13. A nonwoven filtrationmedium comprising: a base media comprising synthetic and/or naturalfibers; and microfibrillated cellulose fibers disposed on a surface ofthe base media, wherein the microfibrillated cellulose fibers are notdistributed throughout the base media, and wherein a majority of themicrofibrillated cellulose fibers have a lateral dimension of 700 nm to4 microns; wherein the microfibrillated cellulose fibers are present inan amount sufficient to provide a nonwoven filtration medium having anaverage filtration efficiency that is at least 10% greater than that ofthe base media.
 14. A nonwoven filtration medium comprising: a basemedia comprising fiberglass fibers; and microfibrillated cellulosefibers disposed on a surface of the base media, wherein themicrofibrillated cellulose fibers are not distributed throughout thebase media, and wherein a majority of the microfibrillated cellulosefibers have a lateral dimension range of 700 nm to 4 microns.